1. Field of the Invention.
The invention relates to a continuous passive motion (CPM) system for mobilizing a joint of a patient's limb. In particular, the present invention is a live display apparatus for setting extension and flexion limits of movement in a CPM system.
2. Description of the Prior Art.
Continuous passive motion (CPM) therapy is becoming an increasingly popular form of orthopedic care following an injury, illness, or surgical procedure to a joint of a patient's limb. During CPM therapy an external force is applied to the limb so as to flex and extend the limb, thereby inducing motion of the joint. Continuous passive motion of a joint following injury, illness or surgery has been found to reduce post-operative pain, decrease adhesions, decrease muscle atrophy, and enhance the speed of recovery. These benefits are achieved while minimizing other risks of immobilization such as venus stasis, thromboembolism and post-traumatic osteopenia.
Devices for performing continuous passive motion are well known and disclosed, for example, in the Pecheaux U.S. Pat. No. 4,323,060 and Wright et al U.S. Pat. No. 4,520,827. When in operation, devices of this type will drive the limb between preset flexion and extension limits. Several techniques for selecting the extension and flexion limits are known and used in the prior art. In accordance with one technique, the CPM device will include mechanical stops which limit motion of the CPM device. The stops are manually adjusted to set the extension and flexion limits. A second technique involves the use of switches, such as thumbwheel switches, which are actuated to provide electrical indicia of desired extension and flexion limits.
In the prior art techniques described above, an operator, such as a clinician, will evaluate the patient's condition and make an "educated guess" as to what the proper extension and flexion limit positions should be. The mechanical stops or switches are then set accordingly. These techniques do not take into account the patient's response, or physiological reaction, to the therapy. If after observing the patient it is determined that the preselected limits are incorrect, the operator must readjust the switches or mechanical stops. This procedure is repeated until proper extension and flexion limit positions are established.
There is a continuing need for improved apparatus for setting extension and flexion limit positions in CPM devices. Such an apparatus will preferably permit a clinician to observe the patient while the extension and flexion limit positions are being established. A "live" display apparatus of this type will permit the clinician to observe the physiological effects of the CPM therapy on the patient, thereby permitting a more accurate setting of extension and flexion limit positions. A device of this type would clearly be far more convenient to use than those of the prior art.